Good Dog: Studies & Research
The influence of each species’ feeding ecology
Humans tend to be risk-averse, which is often illustrated by our decision when offered either $100 or the opportunity for a 50-50 shot at receiving either $200 or nothing. In general, humans go for the sure thing. We are not, as a species, risk-prone, or we would gamble on the shot at getting the bigger payoff.
It turns out that a number of studies across a broad range of species have shown that how a species responds to risk is predictable based on their feeding ecology. Animals who depend on erratic, ephemeral food sources, such as meat that they hunt or fruits that are patchy and only ripe for a brief time, tend to be risk-prone. They are willing to gamble on the big payoff. Species that eat diverse types of food or food that is more reliably available, such as vegetation, are risk-averse.
Some of our primate relatives are like us, and some are the opposite. For example, bonobos and lemurs (who both eat a very diverse diet that is mainly vegetarian) are risk-averse like us, choosing a sure thing of lower value over a chance at something better. Chimpanzees and capuchin monkeys—both meat and patchy fruit eaters—are different, being risk-prone and choosing the option that may yield a big reward but could leave then empty-handed. This pattern has appeared in closely-related species birds, too, where those who eat insects are risk-prone, while species who eat seeds are risk-averse.
Scientists haven’t fully explored how widespread this pattern of feeding ecology predicting risk-taking behavior is, but wolves and dogs are an interesting test case. These two species diverged quite recently in an evolutionary sense, but their feeding ecologies differ greatly. Wolves are primarily hunters and dogs are mainly scavengers. Hunting has a high failure rate, but the rewards of a big kill are enormous. In contrast, the source of food for the vast majority of dogs worldwide is human refuse, which tends to be available far more regularly.
In a recent study called “Exploring Differences in Dogs’ and Wolves’ Preference for Risk in a Foraging Task” scientists investigated whether wolves and dogs conform to the pattern seen across so many other species. Based on their different feeding ecologies, they predicted that compared with each other, wolves would be risk-prone and dogs would be risk-averse. The study was done at Wolf Science Centre in Austria, using dogs and wolves who were raised and live at the facility and have had the same overall experiences there.
The subjects of the study were trained to choose either a bowl that contained a dry pellet of food or a bowl that had a fifty percent chance of containing a piece of meat and a fifty percent chance of holding a stone. After each choice, the subject was given the contents of the bowl. All the wolves and dogs in the study were subject to tests to confirm that they understood the choice they were making and also to confirm that they preferred the meat to the dry food pellet.
The researchers found that the pattern of risk-taking seen in other species also applied to wolves and dogs. As expected, wolves were more risk-prone than dogs. However, there is more to this study than that simple conclusion. Wolves learned the system faster than the dogs, and the researchers acknowledge that they may have understood it better than the dogs. Additionally, dogs’ preference for the meat versus dry food pellet was not as strong as it was for wolves. Therefore, the risk of losing out and getting nothing for the chance to get something only a little better than a food pellet may not have been worth it to dogs. There was greater variation among individual dogs in risk-taking strategy compared with wolves, who were more similar in their choices, so it’s possible that there are dogs who are risk-prone as well as dogs who are risk-averse. (Dogs made the risky choice from 38 to 76 percent of the time, while wolves took the risky option 70 to 95 percent of the time.)
Overall, despite the conclusions made from the data in this study, direct comparisons of the choices made by these two species may require further study. It would be very interesting to learn more about decisions to take risks by dogs and wolves in a study with more than seven of each species, though I realize possible subjects for a study such as this are limited. It would also be fascinating to know about the decisions foxes and coyotes would make if presented with the same choices. Comparative research that include dogs as one species among many allow us to learn a great deal about how their evolutionary history and ecology have affected their behavior. It’s one of many ways that we can deepen our understanding of the animals who share our homes and live in our hearts.
Are We Smart Enough to Know How Smart Animals Are?
In Are We Smart Enough to Know How Smart Animals Are? Frans de Waal presents a fascinating history of the study of animal behavior and cognition. De Waal, who says his love of animals dates to his childhood, is a worldrenowned primatologist and ethologist and director of the Living Links Center at the Yerkes National Primate Research Center. We asked him to shift gears and give us his take on the canine mind.
Bark: Konrad Lorenz (co-founder of your field) wrote Man Meets Dog in 1954. And while it is still one of the best, if slightly flawed, books on canine behavior, why did it take so long for ethologists, and other researchers, to to study dog behavior?
Frans de Waal: Dogs were (and are) considered imperfect subjects of study because they are “unnatural.” Many ethologists, including Lorenz, feel that natural behavior under naturalistic conditions is what we should focus on, and the dog is a product of artificial breeding. Lorenz liked all animals, however, and so couldn’t resist describing his dog stories, and we should all be grateful.
Clearly, the dog is a mammal with many typical mammalian tendencies, so now scientists are finally seeing that the fact that they are domesticated also has advantages. For example, they are eager to work with us, they are generally not dangerous, they are smart, they have empathy. Lots of great things can be done with them. And they are easier to work with than other large mammals, such as apes and dolphins.
Bk: Can you give an example of how other species, including dogs, demonstrate empathy?
FdW: American psychologist Carolyn Zahn-Waxler sought to determine at what age children begin to comfort family members who sobbed or cried “ouch.” It turns out that children do so at one year of age. In the same study, Zahn-Waxler accidentally discovered that household dogs react similarly. Appearing as upset as the children by the distress-faking family members, the dogs hovered over them, putting their heads in their laps with what looked like great concern. This work has recently been repeated in different studies, more focused on the dogs themselves, and it is clear that these animals show empathic concern for humans.
The ancestor of the dog, the wolf, probably behaves the same. If “man is wolf to man,” as Thomas Hobbes liked to say, we should take this in the best possible way, including a tendency to comfort the whimpering and help the needy. This insight, of course, would undermine much of political philosophy based on Hobbes’ dog-eat-dog view of nature.
Bk: Do you think human bias has played a part in some of the canine cognitive studies?
FdW: At first, dogs were rated as more intelligent than even apes and wolves because they followed the direction of human pointing (at a bucket with food), whereas apes and wolves ignored human directions. Then it was found that wolves raised in a human home will act more like dogs, following human pointing, suggesting that the earlier failures with wolves were probably due to lack of bonding and attention. The same probably applies to the apes. Now, dogs are seen not just as smart but rather, as finely in tune with the species that bred them.
They have a special bond with us, as also reflected in the oxytocin studies, which show that human-dog contact increases this “cuddle” hormone in both. The dog is perhaps the only animal that performs at its peak when tested by humans, whereas many other animals are not so into us, hence need to be tested in different ways. This is yet more proof that cognitive testing of animals always needs to take into account what kind of animal we are dealing with: we need to find the most species-appropriate way.
Bk: In contrast to behaviorism’s reward/ punishment model, ethology views animals as “seeking, wanting and striving.” Why do you feel the latter is a more productive way to look at animals?
FdW: The behaviorists (followers of B. F. Skinner) totally overlooked natural animal tendencies. Trying to explain all behavior on the basis of reward and punishment, they could not explain why you can train a dog to fetch, but not a rabbit or a goat.
Predators are obsessed with small moving objects, which we see every day in our dogs as well as cats. Their interest sets up a learning situation where they are going to absorb many lessons about how to catch these moving objects, how to trick them, how to outsmart them. Dogs eagerly learn all of those things.
Reward and punishment are only small parts of the story; their natural hunting instinct is, in fact, the driver of the process. This is where behaviorism failed. It had some good ideas, many of them applicable to animal training, but its perspective was far too narrow as it lacked attention to natural tendencies and the evolution of behavior.
Bk: Why do you think Darwin used dogs to illustrate emotional continuity?
FdW: Darwin was a dog lover, and he knew that to get his message across about the continuity between human and animal emotions, the dog would be the easiest way to communicate. Darwin mostly worked on the expression of emotions (it’s hard to know what animals feel, but we can at least document how they signal various states, such as fear, submission, anger, affection). Of course, the dog is very expressive with its postures, facial expressions, tail-wagging, growling and so on. Darwin knew that most people could relate to all of this, and would have more trouble if he described other species that people have less exposure to.
Bk: In terms of an evolutionary advantage, how important is it for a species to have self-awareness, or theory of mind?
FdW: These capacities require large brains. In terms of recognizing oneself in the mirror or understanding what others know, the champion species are apes, dolphins, elephants and perhaps also the corvids (crow family). This doesn’t mean that dogs lack them. They probably have similar understanding, but not as fully expressed.
The more complex the societies of a species, the more demands there are on cognition, and perhaps canines do not need social understanding at the level of an ape or dolphin. I feel we need to judge animals on what they are good at and what they need to know to survive. In this regard, canines have lots of specialized skills, often related to their sense of smell, their pursuit of prey, their need for tight cooperation and so on. This is where we should test them out, and probably find remarkable skills.
Bk: Clearly, emotions are important to the understanding of behavior; how do they relate to and inform one another?
FdW: In my book, I left emotions out on purpose because I felt it would muddle things. But there can be no studies of cognition without attention to the emotions, and vice versa. The two go hand in hand. In our famous capuchin monkey experiment with the grape and the cucumber, for example, you can see not only that the monkeys judge what they get relative to what others get, but also their strong emotional response. You cannot study the one and ignore the other.
Good Dog: Studies & Research
What you say and how you say it both matter
Humans use both words and the intonation of speech to decipher the meaning of language, and it turns out that our dogs do, too. In a research paper called “Neural mechanisms for lexical processing in dogs” scientists investigated how dogs process the meaning of language. They found that dogs’ brains have even more in common with humans’ brains than previously thought. (It’s not clear when we will collectively stop being surprised by this, but I hope we always remain excited about new evidence to explain why we feel that dogs are kindred spirits.)
In this study, dogs who have been trained to remain still while their brain activity is recorded listened to recordings of their trainers talking. There were four types of recordings: 1) words of praise spoken with intonation typically associated with praise, 2) words of praise spoken with a neutral intonation, 3) neutral words spoken with intonation typically associated with praise, and 4) neutral words spoken with a neutral intonation.
Researchers analyzed the brain activity of the dogs in response to each of the recordings, and came to several conclusions about the way that dogs respond to words and the intonation of human speech. The dogs processed the vocabulary in the left hemisphere of their brains, which is where humans also process the meaning of words. The dogs processed the intonation of the words separately, in a different region of the brain. Just as humans do, dogs processed the intonation of human speech in the right hemisphere of their brain. Dogs also process sounds that convey emotion without words in this same region of the brain’s right hemisphere.
Dogs process both words and the intonation of human speech to decipher meaning. Just as humans do, they process these two aspects of speech separately, then integrate them to determine the full meaning of what was said. Only the praise that was spoken like praise—higher pitched than normal speech and with more variation in pitch—activated the reward centers of dogs’ brains. Though they may understand words of praise said in any manner, it only makes dogs happy to hear us praise them when we do it with proper feeling.
This research does more than reveal yet another similarity in the way that human and dog brains process information. It also suggests that the ability to connect a word to a meaning did not develop with the evolution of spoken language. Rather, it is a more ancient ability that can be made use of in the context of the human-dog relationship to link specific sounds to specific meanings.
The take away messages from this research are that dogs process two parts of spoken language—words and intonation—the same way that humans do and if you want to make your dogs happy, you have to praise them like you mean it!
Good Dog: Studies & Research
Beliefs do not substitute for data
Watching dogs play is very exciting, and there has been a lot empirical research on how and why dogs (and other animals) engage in this activity with boundless zeal. A number of people have asked me to comment about dog play after reading this section in a new book by Raymond Coppinger and Mark Feinstein called How Dogs Work. So, I decided to do so.
The authors begin their chapter 9 on play by claiming, “Hundreds of scientific papers have been written on the subject of ‘play’ behavior—an activity for which dogs are, of course, famous.” Recognizing that there is a solid and growing literature on play—there’s really no reason to put the word play in square quotes—I assumed that what followed would be a detailed review of this research, but rather, what I discovered was a disjointed discussion of play and not an in-depth review of the scientific literature. Instead, the authors offer their own unpublished observations and the results of unpublished student projects, all of which are impossible to assess.
Do dogs and other animals actually play? Coppinger and Feinstein write that they put the word play in scare quotes because “in spite of the fact that people feel like they know it when they see it, it’s not at all obvious that play is a unitary ‘thing-in-itself’ that can easily be characterized, let alone explained in evolutionary terms.” No one I know who has spent years studying play would argue that play is a “unitary ‘thing-in-itself’,” nor would they agree that play cannot be explained “in evolutionary terms.” Indeed, some of the references the authors include show there are a number of highly plausible evolutionary explanations (and the University of Tennessee’s Gordon Burghardt, who has studied comparative aspects of play for many years and wrote The Genesis of Animal Play, provided the Foreword for Coppinger and Feinstein’s book).
Why do animals play? Briefly, various theories have been offered about why animals play, and there’s no one explanation that fits all examples of animal play. Detailed comparative data show play is important in social development, physical development, and cognitive development. And, neurobiological research strongly suggests play can be pleasurable and fun and animals may simply play because it feels good, “for the hell of it.” Indeed, many researchers are taking fun seriously, and the 25th anniversary issue of the journal Current Biology was devoted to the biology of fun with many play researchers weighing in on the topic. Coppinger and Feinstein write, “We agree that there is good reason to believe that animals derive pleasure from play - indeed they do from all of their motor activities.” (my emphasis) While animals might derive pleasure from play, eating, and sex, it’s difficult to argue they feel good running from competitors or predators, but the necessary research has not been done.
Based on an extensive review of available literature, my colleagues Marek Spinka, Ruth Newberry, and I proposed that that play functions as training for the unexpected by increasing the versatility of movements and the ability to recover from sudden shocks, such as the loss of balance and falling over, and to enhance the ability of animals to cope emotionally with unexpected stressful situations. To obtain this training, we suggested that animals actively seek and create unexpected situations in play and actively put themselves into disadvantageous positions and situations.
Comparative data from a wide range of species support this hypothesis. And, while it is difficult to test these ideas in the field, a study of mountain goat kids by Rachel Théoret-Gosselin, Sandra Hamel, and Steeve D. Côté called “The role of maternal behavior and offspring development in the survival of mountain goat kids“ showed that “play behaviors could enhance the emotional resilience to stress not only for unpredicted events but also in stressful group situations because play could reduce aggressiveness in gregarious species.” More field data are needed and this study is an excellent example of what needs to be done.
The play bow: Are dogs really confused when they play and what does this mean?
The authors also dismiss the detailed work that has been conducted on the play bow, a highly ritualized and stereotyped action by which animals signal their intention to play (please see accompanying image). When dogs and other animals bow they crouch on their forelimbs, raise their hind end, and occasionally wag their tail and bark. Coppinger and Feinstein write, “But we wonder if the so-called play bow in fact really has any adaptive, let alone cognitive, significance.” A good deal of very detailed research has been conducted on the bow by my research group and also by Barbara Smuts and her students that clearly supports the claim that bows are adaptive and have cognitive significance (please also see along with Mechtild Käufer’s excellent book called Canine Play Behavior: The Science of Dogs at Play and a comprehensive review essay by Elisabetta Palagi and eight other play experts called “Rough-and-tumble play as a window on animal communication“). The abstract for this excellent evidence-based and extremely significant up-to-date essay reads: Rough-and-tumble play (RT) is a widespread phenomenon in mammals. Since it involves competition, whereby one animal attempts to gain advantage over another, RT runs the risk of escalation to serious fighting. Competition is typically curtailed by some degree of cooperation and different signals help negotiate potential mishaps during RT. This review provides a framework for such signals, showing that they range along two dimensions: one from signals borrowed from other functional contexts to those that are unique to play, and the other from purely emotional expressions to highly cognitive (intentional) constructions. Some animal taxa have exaggerated the emotional and cognitive interplay aspects of play signals, yielding admixtures of communication that have led to complex forms of RT. This complexity has been further exaggerated in some lineages by the development of specific novel gestures that can be used to negotiate playful mood and entice reluctant partners. Play-derived gestures may provide new mechanisms by which more sophisticated communication forms can evolve. Therefore, RT and playful communication provide a window into the study of social cognition, emotional regulation and the evolution of communication systems.
The so-called play bow. Based on an unpublished student project in which “Border collies were confronted with normal and drugged roosters”, Coppinger and Feinstein believe that the “so-called play bow” is a posture assumed by an animal confused by its next move. They write, “... the play bow occurs when an animal is in a temporarily indeterminate state ... In short, the ‘playing’ animal is in conflict about its next move - and the play bow in fact looks just like a combination of multiple conflicting behavioral shapes.” The authors ignore detailed research that shows how play bows are extremely stereotyped (they are what ethologists call a modal action pattern), they vary in shape and duration depending on where they are performed in a play bout, and they allow a dog to perform a wide variety of movements from this posture. There are no data that support their belief and the student’s data are impossible to assess. And, it’s not clear at all why they refer to the “so-called play bow,” when many researchers have studied it and concluded, based on substantial data, that it is indeed used almost exclusively in the context of play both as a play invitation signal and also to maintain the play mood.
Let’s briefly think about what it means when a dog or other animal is confused, because every definition I can find indicates that there have to be cognitive and emotional underpinnings. In the case of dog-dog play, a simple view would be that Harry (a dog) wants to play with Mary (another dog) and that Harry isn’t sure what to do so he carefully pays attention to what Mary has done and is doing, and tries to factor this information into what she is likely to do in the future. In essence, Harry is pondering if he chooses to do “X” or “Y,” what will Mary do (and, of course, vice versa). Because play is indeed a hodge-podge of various actions, a kaleidoscopic behavior, on the authors’ view, Harry is confused, and to overcome his confusion he performs play bows.
There are no data that support the belief that dogs are confused when they play, however, there are data that show that there is a good deal of rapid of thinking and feeling on-the-run based on what Harry thinks and feels Mary is likely to do during the on-going interaction (and vice versa). These sorts of interactions make it clear that play is also a good place to observe and to study what researchers call a “theory of mind,“ because Harry and Mary need to pay very close attention to what each has done and is doing, and how that will influence what she or he is likely to do in the future (for further discussion please see Alexandra Horowitz’s essay called “Attention to attention in domestic dog (Canis familiaris) dyadic play“). There is a good deal of mind-reading going on here as Harry and Mary make careful and rapid assessments and predictions of what their play partner is likely to do.
The cognitive and emotional underpinnings of “being confused” are rather rich, and do not lend themselves to simple mechanistic explanations that are favored by the authors. Available and ample data for a number of different species show there are predictable rules of play that cross species lines, namely, ask first, be honest, follow the rules, and admit you’re wrong. This is why play is so exciting to engage in and also so much fun to watch and to study. And, this is also why play among young and old dogs only rarely escalates into injurious aggression, although the authors recall an instance when play among four-week-old Border collie littermates was fatal and use this observation to claim that play “can itself cause significant harm” (p. 165). Indeed, Shyan, Fortune, and King (2003) reported that fewer than 0.5% of play fights in dogs developed into conflict, and only half of these were clearly aggressive encounters. Their data agree with our own observations on wild coyotes and free-running dogs at play.
Behavioral variability. Another example of a claim that is countered by available data centers on behavioral variability in young dogs and wolves. Coppinger and Feinstein write, “When we observe wolves, we see a similar picture. Wolf puppies are often noticeably more robust and varied in their play routines than dogs of the same size and age. This means, according to our hypothesis, that they should have more available motor patterns than the dogs do. That is in fact the case.“ (my emphasis) However, they offer no data.
Along these lines, years ago Robert Fagen, another play expert and author of the classic book Animal Play Behavior, analyzed the sequential variability of play and aggression in young dogs (beagles), wolves, and coyotes using data my students and I collected, and discovered that social play in the beagles was more variable than social play in wolves and coyotes of the same age (and coyote play was more variable than wolf play). These data were published in an essay I wrote with John Byers (“A critical reanalysis of the ontogeny of mammalian social and locomotor play: An ethological hornet’s nest,” in K. Immelmann, G. W. Barlow, L. Petrinovich, and M. Main, Eds., Behavioral Development, The Bielefeld Interdisciplinary Project. New York: Cambridge University Press, pp. 296-337, 1981) that the authors list in their reference section. And, we also found that young beagles and wolves shared the same basic ethogram and number of motor patterns. Perhaps working dogs such as Border collies are different from beagles and other dogs, but we really don’t know if this is the case.
The way in which the authors routinely dismiss a wealth of detailed research on animal play is characteristic of much of their book, that is essentially a tapestry of criticism using stories and unpublished projects in lieu of published data. It’s easy to see how one might walk away feeling that just about everyone else is wrong about dog behavior, cognition, emotions, and consciousness, and much of the research that has been done can be tossed into the garbage because it’s merely debris.
All in all, the one-sided assault on the ever-growing literature in the growing field called cognitive ethology (the study of animal minds) fails. How Dogs Work does not really tell us how dogs work, but rather provides an extremely narrow view of mainly working dogs as machines. I find the topic to be of great interest and am always eager to learn more about why some people favor reductionist and mechanistic accounts to explain the behavior of complex sentient beings (see, for example, Sara Shettleworth’s book, Fundamentals of Comparative Cognition). However, How Dogs Work doesn’t convince me that the authors’ over-arching views are tenable. Beliefs don’t substitute for data that have been reviewed by peers, and there are plenty of data that are readily available.
All in all, we really know far more than the authors offer, and for numerous wide-ranging and critical discussions of many different aspects of dog behavior I suggest Domestic Dog Cognition and Behavior: The Scientific Study of Canis familiaris edited by Alexandra Horowitz, Adam Miklosi’s Dog Behaviour, Evolution, and Cognition, The Social Dog: Behavior and Cognition edited by Juliane Kaminski and Sarah Marshall-Pescini, and Mechtild Käufer’s Canine Play Behavior: The Science of Dogs at Play. For more on play I highly recommend the excellent and comprehensive review article by Elisabetta Palagi and her colleagues called “Rough-and-tumble play as a window on animal communication“ and (in addition to the references above) Sergio Pellis and Vivien Pellis’ The Playful Brain: Venturing to the Limits of Neuroscience.
What’s so incredibly exciting about the study of play behavior and the cognitive and emotional lives of dogs and other animals is how much we’re learning about how individuals negotiate challenging and complex social and non-social situations by carefully analyzing what’s happening and by using hard-wired actions when needed (for example, when they need to do the right thing instantaneously or the first time they are faced with a specific situation and there’s no room for error), along with behavior patterns that require careful thought and flexibility motivated by what individuals are feeling about the situation in which they find themselves.
Please stay tuned for more on dog behavior, cognition, and emotions, because there is a lot of research being done by research groups around the world, and we still have a lot to learn. Dogs are amazing sentient beings who challenge us in many different ways.
I thank a number of people for help with this essay.
Note: In a number of email messages I've been asked if I knew what happened to the 1000’s of sled dogs dogs for whom Dr. Coppinger was responsible. On page 25 we’re told, “Some four thousand dogs ‘went through the yard’” when “Ray spent fifteen years breeding and training dogs that pull sleds.” I have no idea what happened to these dogs, but according to some people I consulted, this is an incredibly large number of dogs, an average of around 267 a year.
Wellness: Healthy Living
Toxic chemicals also found in dog food
A long-term study conducted in Britain has found that male dogs are losing fertility, and that exposure to environmental chemicals (ECs) that have leached into the environment may be to blame.
The dogs—Labradors, Border Collies, German Shepherds and Golden Retrievers bred to aid the disabled—made an ideal group to explore the larger question of a decline in human semen quality that has been occurring since long before this study.
This twenty-six year long study, 1998-2014, was conducted by Richard Lea and colleagues at Nottingham University’s school of veterinary medicine. They collected annual samples of semen from dozens of dogs, all from the same breeding program, all healthy and well cared for. Each year, the same problem recurred; a 2.4 percent dip in sperm motility, that is the ability to swim in a straight line. In addition to monitoring semen quality, they analyzed health records, finding an increase in cryptorchidism, a condition in which the testicles fail to extend normally to the scrotum. Over the same years, fewer male pups were born than females, also there was an increase in fetal and prenatal female mortality.
And, lurking in the samples of semen and testicles of dogs obtained from neutering, it found ECs—chemicals that tamper with hormones. The chemicals include polychlorinated bisphenol (PCB), a compound banned in 1977, and diethylhexyl phthalate (DEHP). PCBs don’t readily break down while phthalates are common in a wide number of products, from cosmetics to detergent. Both chemicals are associated with fertility issues and birth defects.
In human babies, exposure to chemicals has been linked to faulty development of semen quality and cryptorchidism. According to the study, such reproductive problems often cluster in geographical areas, and so are suspected of having a common cause; exposure to hormone-disrupting chemicals is “thought to be the initiator.” To explore the same possibility in dogs, chemicals were measured in canine testes and semen taken from the same geographical area where the study took place.
Both chemicals “perturbed sperm viability, motility and DNA integrity in vitro.” The researchers concluded that the direct effects of chemicals on sperm “may contribute to the decline in canine semen quality” that parallels that in humans.
“Why the dog?” said Dr. Lea. “Apart from the fact that it is a great population of animals to work with, dogs live in our homes, they sometimes eat the same food, they are exposed to the same environmental contaminants that we are, so the underlying hypothesis is that the dog is really a type of sentinel for human exposure.”
The same ECs were found in a range of commercially available dog foods. DEHP and PCB153, “were detected in adult dog testes and commercial dog foods at concentrations reported to perturb reproductive function in other species.”
While the brands were not named, they are reported to be both wet and dry forms sold worldwide. The scientists don’t know how the chemicals made it into the food, but since they are not deliberate additives, they may have leached from the packaging or processing sources.
These overall findings are troubling, but they also noted that: “Amongst the dry dog food samples, one sample designed for puppies (1 to 24 months of age) had higher concentrations … relative to the other samples tested.”
Plus, while the researchers cannot say the dog food is a direct source of the ECs, the New York Times reports that "Dr. Lea said it was probably a major one."
What is known is that the chemicals wound up in dog’s testicles, where they messed with sperm motility and viability. “This may be a way by which environmental chemicals directly affect male fertility.”
While the dogs in the study were still able to reproduce, it’s hardly reassuring that, once more, the dogs who share our homes also share our diseases, unwittingly, acting as the “canary in the mine” for us.
Good Dog: Behavior & Training
Differential use of the left and right nostril
The common wisdom that dogs can smell fear doesn’t give dogs full credit to the nuances of their ability to sense emotion through their noses. A recent study titled “The dog nose “KNOWS” fear: Asymmetric nostril use during sniffing at canine and human emotional stimuli” examined dogs’ tendencies to sniff various substances with the right or the left nostril. Exploring this side bias may seem like looking at random details, but the side of the nose used to sniff something tells us a lot about the dog’s emotional reaction to the odor. The use of one side of the body indicates a differential use of one side of the brain or the other, which is a clue to the dog’s emotions.
The left side of the brain processes more positive emotions such as happiness and excitement as well as stimuli that are familiar. The right side of the brain tends to take over when a dog is processing negative emotions such as sadness or fear as well as novel stimuli. In general, the right side of the body is controlled by the left hemisphere of the brain and vice versa. However, the nose is an exception; the right nostril sends information to the right side of the brain to be processed and the left nostril sends its information to the left side. The findings of this study suggest that the pathways used to process various olfactory stimuli are dependent on more than just whether they elicit negative or positive feelings.
Eight odors were tested—four from dogs and four from humans. The four human odors were collected as sweat from donors who were joyful, fearful, physically stressed, or in a neutral situation. The joyful and fearful states were elicited by movies, and the physical stress odor was collected after donors ran for 15-minutes. The four canine odors were collected from dogs who were happy following a play session with the guardian, stressed by isolation in an unfamiliar place, disturbed by a stranger approaching the car, and dogs who were asleep. The dogs who “donated” odors were different from the dogs whose sniffing behavior was studied.
To further explore the phenomenon of side bias in sniffing, the guardians of the dogs in the study filled out a questionnaire related to each dog’s temperament. During the study, dogs were led to a video camera under which was mounted a Q-tip saturated with various odors. The videos captured the dog’s sniffing behavior so that it was possible to determine a laterality index for each dog for every odor based on the amount of time spent sniffing with each nostril. A laterality index of 1.0 indicated exclusive use of the left nostril and negative 1.0 indicated exclusive use of the right nostril. Dogs’ cardiac activity was also recorded during the tests of each odor.
I’m sure it’s the science geek in me, but I got a kick out of reading the sentence, “Results for nostril use are shown in Figure 2.” Three of the odors elicited consistent sidedness in nostril use and five of them did not. Dogs more frequently used the right nostril to sniff the canine isolation odor. They more frequently used the left nostril to sniff the human fear odor and the odor from human physical stress.
There were two ways in which the results of the questionnaire were correlated with the laterality pattern for a particular odor. The higher a guardian ranked the dog’s fear/aggressiveness to other dogs, the more likely that dog was to use the right nostril for sniffing the disturbed canine odor. This suggests that individual differences in emotional arousal and perhaps even in temperament influence asymmetries in sniffing behavior. Dogs with higher scores for predatory behavior used the left nostril more for sniffing the odor that came from physically stressed humans. This makes sense when we consider that it is structures in the left side of dogs’ brains that are involved in predatory behavior.
Dogs’ brains are every bit as amazing as their noses, as research about both of them reveal!
News: Guest Posts
An international group of scientists proposes dual domestication from wolves.
Among the many hotly debated topics related to the appearance of dogs in the lives of humans is how often and where it first occurred. In their landmark 1997 paper on dog origins, Robert K. Wayne, Carles Vilá, and their colleagues made the case for multiple origins, but many other students of dog evolution, including Peter Savolainen, a co-author on that paper, have repeatedly and strongly argued for a single place of origin.
In this week’s Science magazine (June 3, 2016) [the article is available here, gratis], Laurent Frantz of Oxford University’s ancient dog program, writing for more than a score of his colleagues from institutions around the world, presents the case for dual domestication of Paleolithic wolves in Western Eurasia and Eastern Asia. According to this hypothesis, a now extinct ancestral wolf split into at least two genetically distinct populations on opposite sides of the Eurasian continent where they encountered and joined forces with humans to become dogs.
Frantz and his coauthors pin much of their argument on analysis and comparison of the fully sequenced genome of a 4,800- year old dog unearthed at Newgrange, Ireland, to other ancient and modern dogs and modern wolves. They found it retained “a degree of ancestry” different from modern dogs or modern wolves. Using that and other evidence the researchers argue that the most comprehensive model for the appearance of the dog involves at least two domestication events 15,000 or more years ago. Frantz writes: “The eastern dog population then dispersed westward alongside humans at some point between 6,400 and 14,000 years ago, into Western Europe (10,11, 20), where they partially replaced an indigenous Paleolithic dog population. Our hypothesis reconciles previous studies that have suggested that domestic dogs originated either in East Asia (9, 19) or in Europe (7).”
I asked Greger Larson, co-director of the Oxford project and corresponding author on the paper, just what were the boundaries of “Western Eurasia,” comprised apparently of Europe and the Middle East, and “Eastern Asia?” He answered in an email that the boundaries were left deliberately vague because where wolves became dogs remains unknown, like the date itself.
In Science, Frantz writes: [W]e calculated the divergence time between two modern Russian wolves used in the study and the modern dogs to be 60,000 to 20,000 years ago.” The first number puts the dog in the time when Neanderthal was still the big kid on the European block, raising the possibility that Neanderthal had protodogs or that early modern humans came to Europe with dogs or soon allied with wolves. Either of the first two prospects must have set off alarms in some circles for Frantz cautions that those dates should not be taken as “a time frame for domestication” because the wolves they used may not have been “closely related to the population(s) that gave rise to dogs.”
Fundamentally, this paper is at once a bold attempt to come up with a workable hypothesis to explain the appearance of the dog in human affairs and a tentative step into troubled waters. Left unanswered are virtually all outstanding questions regarding the who, what, when, where, and why of the transformation of wolves to dogs. Geographically all it does is exclude Central Asia. Whether it does so wrongly may depend on how you define Central Asia geographically.
What makes it bold and radical even is the suggestion that early humans and wolves could have gotten together wherever and whenever they met on the trail of the big game they were following. There are many reasons for that including similar social and familial cultures, but humans and wolves could have joined forces to have become more successful hunters. We learn from Wolves on the Hunt: The Behavior of Wolves Hunting Prey by L. David Mech, Douglas W. Smith, and Daniel R. MacNulty (Chicago, 2016) that while wolves appear excellent at finding and trailing game, they are not very good at making the kill, succeeding perhaps half the time. It is dangerous work at which humans with their weapons excel.
Imagine the scene: Human hunters locate wolves on the hunt by watching ravens who are known to follow them. Human hunters move in for the kill and take as many animals as they can. If smart, they might share immediately with the wolves. If not, the wolves might consume what the humans do not carry off or follow them back to their encampment to take what they can.
The rest is a tale of accommodation through socialization—the ability to bond with another being—and all that entails.
This article originally appeared in Psychology Today's Dog's Best Friend, used with permission.
We may think our dog wIll take a treat from any hand that offers it, but a new study by a team of Japanese researchers suggests that may not be the case. Primates engage in something called “social eavesdropping”— essentially, making judgments about others based on interactions that don’t directly affect their own interests. This study tested dogs’ ability to do the same by setting up situations in which the dogs’ owners asked for help in opening a box and were assisted (helper scenario), rejected (non-helper scenario), or ignored (control scenario) as the dogs looked on. After these interchanges, when the dogs were offered treats, they took them randomly from Helper and Control “strangers” but were biased against non-helpers. According to Kazuo Fujita, professor of comparative cognition at Kyoto university and one of the study’s authors, the ability to socially and emotionally evaluate others “is one of the key factors in building a highly collaborative society.” So, another step in the process of understanding how Canis lupus became familiaris: like humans, dogs are able to pick up clues about who to trust and who to avoid.
Culture: Science & History
How Humans and Their Dogs Drove Neanderthals to Extinction
Pat Shipman, PhD, is a retired adjunct professor of anthropology at Penn State and an internationally recognized expert in taphonomy, the study of how living animals are transformed into skeletons, and then fossils. Her scientific training and boundless curiosity lead her to take on the intriguing question of just why Homo neaderthalensis, one of the most successful apex species of hunters who had thrived for millennium in Eurasia, would almost suddenly, anthropologically speaking, become extinct. Her hypothesis: The Invaders: How Humans and Their Dogs Drove Neanderthals to Extinction (The Belknap Press) points to the abilities of both certain wolves and our ancestors to pair up and this gave them the competitive edge in the battle of survival. It is certainly true that this wasn’t done intentionally, but such an evolutionary breakthrough resulted in an alliance that had devastating effects on not just the Neanderthals but on a long species list including the huge woolly mammoth, saber-toothed tigers and Cave bears. Could it be possible “man’s best friend” have been the Neanderthals’ worst nightmare ? Shipman’s thesis starts with Homo sapiens, who in expanding north out of Africa were not only as an invasive species, but the most invasive in history, wreaking ecologically enormous changes throughout continents. The evidence that she relies on, by a meticulous review of the most current archeological research and genomic and genetic studies, can perhaps most readily be seen in the mammoth remains megasites, where the number of kills increases almost exponentially after the first evidence of the wolf-dog–human alliance was discovered. For ten thousand years before the domestication of the wolf-dog, evidence of early humans hunting mega-fauna like mammoth is scant, but with the addition of the superior hunting and tracking talents that wolf-dogs contributed to our projectile throwing ancestors lead not only to more successful kills of large prey but insured the success of our two predatory species. As for the Neanderthal, it wasn’t just simply that humans bested them as hunters but climate change was also a key contributing factor: but the combo of the alliance of the apex predators with the ice age ensured their extinction, so goes evolution. As Shipman notes about the Jagger Principle, “… the immortal words of Mick Jagger (yes that one) and Keith Richards are the best statement I know of to describe evolution. Things don’t stay the same; you can’t always get what you want; but with a little flexibility, you might get what you need to survive.” This is truly a fascinating and thought-provoking book, and Shipman presents a compelling argument for how canines and humans proved their flexibility and how this could have been the main reason that we survived and the Neanderthals didn’t. But drawing upon the wisdom of another ’60s duo, we also got by with a little help from our [first] friends. See the following interview with Dr. Shipman to learn more.
Bark: How long did it take humans, once they migrated out of Africa, to team up with wolves, a species that was unknown in Africa?
Pat Shipman: There were wolves in North Africa, but my guess is that humans did not team up with them but rather, based on genetic information, with European wolves. The earliest humans in Europe date to perhaps 42,000 years ago. The earliest wolf-dogs we know at present show up about 34,000 years ago (or about 37,000, if the raw radiocarbon date is calibrated for irregularity in the deterioration of C-14). Thus, it may have taken 6,000 years, or less—I seriously doubt we have found the first wolf anyone ever attempted to domesticate.
BK: What environmental reasons led to this amazing partnership?
PS: There were many different predators in Europe when modern humans arrived; competition for prey was considerable, and even worse once humans came on the scene. The idea of domesticating any animal was completely unknown, but somehow— probably by accident—some wolves began cooperating with some humans because the alliance benefited both.
They caught more prey, faster, with less risk to canine or human, which meant more energy for reproduction. Wolves had a set of skills for hunting in packs: speed, keen ears, a very keen sense of smell, sharp teeth and claws. Early humans were much slower, had lousy senses of smell and hearing, and blunt teeth, but they had distance weapons that could kill an animal while avoiding injury from close contact. By teaming up with special wolves—wolfdogs they could capture a much wider array of animals with much less risk and less expenditure of energy. They were nearly unstoppable.
BK: You write that proto-dogs were like “living tools” to humans. Was this a mutually beneficial arrangement?
PS: Absolutely. You cannot force any animal to cooperate if it does not want to. You cannot force an animal not to be hostile to humans or to cooperate with humans if there is no benefit to the animal.
BK: Wolves are highly territorial, and may kill other wolves who come into their area. Since this was well before human settlements, humans and wolf-dogs would have traveled great distances, through other species’ (i.e., wolves’) territory. Could the advantage to the wolfdogs come from the protection offered by their human partners?
PS: Both wolf-dogs and humans were more efficient hunters through cooperation— the wolf-dogs by having hunters kill the prey from a distance after they had found it, isolated it and stressed it through charging and holding it at bay.
For wolf-dogs and humans to travel together, they must have cooperated to drive off or kill the wolf packs through whose territories they passed. Indeed, there is a marked rise in the number of wolf bones in human sites after wolf-dogs appear. I think wolves were deliberately targeted by humans in order to protect the wolf-dogs, and to protect the remains of their kills from scavengers.
BK: Why do you think that Neanderthals did not also have wolf-dogs?
PS: One quite real possibility is that modern humans had adaptations that fostered better communication with wolf-dogs and possibly (we don’t know) Neanderthals did not. For example, humans are the only primates with whites to their eyes, which makes communicating the “direction of gaze”— where you are looking—very obvious. This is a huge advantage in silent cooperative hunting. We do not yet know if Neanderthals had this adaptation or not. Assuming that they saw humans working with wolf-dogs, why Neanderthals did not steal them or make their own is unclear. Humans undoubtedly prized the canines and may have gone to great lengths to prevent them from being stolen. Maybe Neanderthals did not have the empathy and ability to understand wolf-dogs that is so necessary to a good working relationship. Maybe Neanderthals tried and just couldn’t figure out how to handle them.
BK: What do you think inspired humans to see that teaming up with wolves might give them a competitive edge? Did it have to do with their diet perhaps?
PS: I don’t think humans set out to domesticate wolves into dogs; I think it was an accident based on taking in orphaned puppies and raising them. Before working with wolf-dogs, humans were rarely able to kill mammoths or other very large game; afterward, there are sites with dozens of mammoth kills. I suspect that killing mammoths efficiently and regularly required the help of wolf-dogs, so mammoths weren’t really a preferred human food until humans had wolfdogs to help.
BK: It was interesting that the primary protein source in the bones of both wolfdogs and humans can be detected. What does that tell us?
PS: First, this sort of study tells us that, at the same site, wolf-dogs and wolves ate different prey animals predominantly. (That is a very surprising finding if my colleagues and I are mistaken and the wolf-dogs are really wolves, that would make them a very odd and distinctive group.) Second, this type of study shows us that humans may have provisioned wolf-dogs, rather than letting them simply eat whatever was left over.
BK: You say that wolf-dogs were a first, but unsuccessful, attempt at domestication; and that domestication happened several times in different areas. Are you concerned that their mtDNA (mitochondrial DNA) evidence hasn’t been found in modern-day canids?
PS: Not at all. There is as much mtDNA evidence that these identified wolf-dogs were wolves as there is that they were dogs: none. The mtDNA we have so far from wolf-dogs is unique, previously unknown. What that means is uncertain.
This particular genetic material is passed from mother to daughter to granddaughter and so on; the father’s mtDNA is not. This means that if you have a small population with an unusual mtDNA, the probability that it will go extinct in 1,000 years—much less 35,000—is very, very, very high.
It could be as simple as a few females who don’t reproduce successfully or have only males due to random chance. Also, athough we have several thousand mtDNA lineages from living animals, there are millions of dogs and wolves whose mtDNA is unknown. Maybe the sample sizes of living animals are too small and the wolf-dog mtDNA is still out there somewhere. Maybe it is simply extinct.
The standard calculation is that 99 percent of all mtDNA lineages go extinct, so we can’t conclude too much from that. I am not at all worried that the mtDNA information from wolfdogs has not yet been matched in any other group. Also, the entire wolf-dog group may well have gone extinct, with a still-later domestication of wolves into dogs. We just don’t know.
Good Dog: Studies & Research
Seeing eye to eye
How better to spend a chilly winter afternoon than gazing into a pair of warm canine eyes? As it turns out, there’s a perfectly rational reason to do so, one that also suggests how dogs became our “truest companions.”
In a 2015 study reported in Science (“Oxytocin-gaze Positive Loop and the Coevolution of Human-Dog Bonds”), a team of Japanese researchers led by Miho Nagasawa studied the role oxytocin plays in the ancient relationship between people and dogs. Popularly called the “love” or “cuddle” hormone, oxytocin enhances the attachment between human mothers and infants; the longer the two gaze into one another’s eyes, the greater their levels of oxytocin. The practical effect of this feel-good neurological chemical is to stimulate contact. For mother and child, the shared gaze creates a seamless loop of affection and bonding.
Since both dogs and humans use gaze to communicate, the team hypothesized that this same loop might come into play between our two species. It could also help explain how dogs came to take their place in our lives—or, in science-speak, to suggest a reason for our unique “interspecies affiliation.”
The study’s results seem to confirm the hypothesis. In a series of experimental situations, dogs’ “gazing behavior” increased oxytocin levels in their owners, and when the owners gazed back, the dogs’ oxytocin levels went up as well. And, as with human mothers and infants, the amount of time owners talked to and touched their dogs also increased, thus deepening the bond between them.
So, the next time you find yourself engaged in a mutual-admiration session with your co-pilot, remember: it’s not just a pleasant way to pass the time, it’s also part of nature’s grand plan!
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